Printed built-in antenna for use in a portable electronic communication apparatus

ABSTRACT

An antenna for use in a portable electronic communication apparatus has a pattern of a conductive material. The pattern of conductive material is printed on the Printed Circuit Board (PCB) ( 7 ), comprising the RF circuitry of the portable electronic communication apparatus, to which antenna pattern is connected. The pattern comprises a first and second antenna arm, which together for a PIFA antenna and are resonating in a first and second frequency band, respectively. As an alternative, the antenna pattern forms a multi-port antenna having separate antenna arms for Rx and Tx, respectively.

RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 national phase applicationof PCT International Application No. PCT/EP03/04298, having aninternational filing date of Apr. 25, 2003 and claiming priority toEuropean Patent Application No. 02009863.8, filed May 2, 2002, and toU.S. Provisional Application No. 60/379,138 filed May 9, 2002, thedisclosures of which are incorporated herein by reference in theirentireties. The above PCT International Application was published in theEnglish language and has International Publication No. WO 03/094289 A1.

TECHNICAL FIELD

The invention relates to an antenna for use in a portable electroniccommunication apparatus such as a mobile telephone. More specifically,the invention relates to a built-in antenna comprising a pattern ofconductive material, which is printed on the printed circuit board (PCB)of the portable electronic communication apparatus. The invention alsorelates to a portable electronic communication apparatus comprising sucha printed built-in antenna.

PRIOR ART

A portable electronic communication apparatus, such as a mobiletelephone, requires some sort of antenna in order to establish andmaintain a wireless radio link with another unit in the communicationsystem, normally a base station. In the telecommunication industry, thedemand for mobile telephones that are small in size, light in weight,and inexpensive to manufacture are continuously present. To this end,printed built-in antennas are utilized for mobile telephones within the300–3000 MHz frequency range. Printed built-in antennas known in the artcomprises microstrip patch antennas and planar inverted-F antennas(PIFA).

As the mobile telephones becomes smaller and smaller, both conventionalmicrostrip patch and PIFA antennas are still too large to fit smallmobile telephone chassis. This is particularly problematic when the newgeneration of mobile telephones needs multiple antennas for cellular,wireless local are network, GPS and diversity.

The antenna pattern of the antennas according to the above are printedon a support member separated from the main printed circuit board (PCB)of the mobile telephone. After manufacturing, the antenna can beconnected to the PCB by utilizing connectors, such as pogo-pins.

Disadvantages of built-in antennas known in the art are that both theconnectors and the assembling of the antenna and the PCB addconsiderable cost to the mobile telephone. Also, the mechanicaltolerances involved in the assembling of the conventional built-inantenna and the PCB effect the performance of the antenna negatively.That is, it is difficult to obtain exactly the same position of theantenna in relation to the signal source, and sufficient connection ofthe pogo-pins. Also, in antenna configurations known in the art, thespace between the antenna and the PCB is not utilized effectively, bye.g. positioning electronic components in between them.

Further, as it becomes more and more common with multi-port antennas inportable electronic communication apparatuses, i.e. antennas havingseparate antenna arms for each Rx (receiver unit) and Tx (transmitterunit), the number of connectors is increasing and consequently the costand the problem with mechanical tolerances.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a built-in antennahaving a printed pattern of conductive material with good radiationcharacteristics in at least one frequency band, which is inexpensive tomanufacture and utilizes the interior space of an electroniccommunication apparatus effectively. More specifically, it is an objectof the invention to provide an antenna, which can be connected to the RFcircuits of the printed circuit board (PCB) of the apparatus without anyconventional connectors, such as pogo-pins. A further object of theinvention is to eliminate the mechanical tolerances involved with theassembly of the antenna and the PCB.

Another object of the invention is to provide a portable electronicapparatus comprising a PCB and a built-in antenna, which can beconnected to said PCB without any connectors.

The above objects are achieved by providing an antenna adapted to bebuilt-in and used in a portable electronic communication apparatus. Theantenna comprises a pattern of a conductive material printed directly onthe PCB of the portable electronic communication apparatus, whichcomprises the RF circuits of the apparatus. Further, the above objectsare achieved by providing an extended ground plane connected to the mainground plane of the PCB and situated parallel to and opposite theantenna pattern. The antenna pattern and the extended ground plane arepositioned with a distance in relation to each other, and form a space,in which low profile electronic components can be positioned.

The above objects are also achieved by a portable electroniccommunication apparatus comprising a PCB having RF circuits connected toan built-in antenna, which is printed on the PCB of the apparatus andconnected to the RF circuits. Also, the apparatus of the inventioncomprises an extended ground plane, which provides good radiationcharacteristics for the antenna.

By providing the inventive antenna manufacturing costs of the portableelectronic communication apparatus is lowered and the interior space ofthe apparatus is utilized more effectively.

As an alternative, the antenna pattern can be provided to form amulti-port antenna comprising antenna arms having four connections tothe circuitry of the PCB. In this embodiment the cost savings inrelation the known art will be even bigger. Also, as no connectors, suchas pogo-pins are needed, the insertion loss is lowered. Further, byproviding separate antenna patterns for the Rx and Tx circuitsrespectively, it is possible to connect the antenna to the Rx and Txcircuitry respectively, without having an antenna switch, which willlower the cost of the mobile phone even more.

Further preferred features of the invention are defined in the dependentclaims.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps, components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described inmore detail with reference to the accompanying drawings, in which:

FIG. 1 shows a mobile telephone having a built-in antenna according tothe invention;

FIG. 2 illustrates a PIFA antenna printed on the main PCB of the mobilephone in FIG. 1;

FIG. 3 illustrates a multi-port antenna printed on the main PCB of themobile phone in FIG. 1; and

FIG. 4 is a SWR diagram and a Smith chart representing the performanceof the embodiment shown in FIG. 2.

DETAILED DISCLOSURE

FIG. 1 illustrates a mobile telephone 1 as one example in which theprinted built-in antenna according to the invention may be used.However, the inventive antenna may be used in virtually any otherportable electronic communication apparatus, in which a built-in antennais preferred.

The mobile telephone 1 shown in FIG. 1 comprises a loudspeaker 2, akeypad 3, a microphone 4, and a display 5 as is generally known in theart. Further, the mobile telephone 1 comprises the antenna according tothe invention, which is built-in into the chassis of the mobiletelephone 1.

FIG. 2 illustrates a multi-band printed built-in antenna according to afirst embodiment of the invention. The antenna comprises a pattern ofconductive material printed directly on the main printed circuit board(PCB) 7 of the mobile telephone 1. In FIG. 2, the PCB 7 is shown asending at the beginning of the antenna pattern. However, as is apparentto the man skilled in the art, this is only for illustrative purposes.In a real application the PCB 7 extends over the full extension of theentire antenna pattern, as the antenna pattern is printed on the PCB 7.

In the embodiment of FIG. 2 the antenna pattern comprises at a firstplane a dual-band PIFA (Planar Inverted-F Antenna) antenna having afirst arm 8 and a second arm 9, which are resonant in a first and secondfrequency band, respectively. Also, to provide a third frequency band,at which the antenna is resonant, the antenna pattern comprises aparasitic element 10, which is capacitively coupled to the main PIFA.Further, to provide good radiation characteristics, e.g. directedradiation, and a ground plane under the antenna pattern an extendedground plane 11 is provided at a second plane, essentially parallel tothe first plane and opposite the antenna pattern.

The first and second antenna arms 8, 9 of the conductive pattern areprinted directly on a first side of the main PCB 7. The main PCB 7 has amain ground plane, to which the second antenna arm 9 is connected. Thefirst antenna arm 8 is connected to the RF port 13 of the main PCB 7.The connection between the antenna pattern and the patches of the PCB 7is e.g. provided by connection strips, which provide sufficientconnection between the antenna and the RF circuits of the PCB to nothave an effect on the antenna tuning such as impedance matching andbandwidth. By printing the conductive pattern of the antenna directly onthe main PCB 7, it is possible to connect the antenna arms 8, 9 to a RFport 13 and ground plane of the PCB 7, respectively, without anyconventional connectors, such as pogo-pins. The RF circuitry of themobile telephone 1 as such forms no essential part of the presentinvention and is therefore not described in detail herein.

As will be readily realized by the man skilled in the art, the RFcircuitry will comprise various known HF (high frequency) components andbase band components suitable for receiving a frequency signal,filtering the received signal, demodulating the received signal into abaseband signal, filtering the baseband signal further, converting thebaseband signal to digital form, applying digital signal processing tothe digitized baseband signal (including channel and speech decoding),etc. Conversely, the HF and baseband components of the radio circuitrywill be capable of applying speech and channel encoding to a signal tobe transmitted, modulating it onto a carrier wave signal, supplying theresulting HF signal to the antenna, etc.

In the first embodiment shown in FIG. 2, the antenna is designed to havean input impedance of 50 ohm, without any impedance matching circuit.The first antenna arm 8 is designed to be resonant in a first frequencyband at around 900 Mhz (GSM), and the second antenna arm 9 is designedto be resonant in a second frequency band at around 1800 Mhz (DCS).However, the design and tuning of the embodiment in FIG. 2 is onlyexemplifying, and is not considered to limit the scope of the invention.Other designs of the printed antenna arms are equally well possiblewithin the scope of the invention.

As an option, the antenna in FIG. 2 comprises the parasitic element 10,which is printed on a second side of the main PCB 7. Therefore, in thisembodiment the main PCB is at least a dual-layer PCB. The parasiticelement 10 is connected to the ground plane of the PCB 7, by e.g. aconnection strip, and capacitively coupled to the main PIFA. Since themain PIFA and the parasitic element 10 are positioned on opposite sidesof the PCB 7, the distance between them is the thickness of the PCB.

For tuning purposes of the bandwidth of the antenna, the parasiticelement is positioned with a longitudinal displacement opposite theantenna pattern of the first side of the PCB 7 as can be seen in FIG. 2.Also, the length of the parasitic element 10 will effect the naturalfrequency of said element 10 and the bandwidth of the antenna. Theparasitic element 10 widens the bandwidth of the second antenna arm 9,which adds the third frequency band, at which the antenna is resonant.Here, the third frequency band is at around 1900 MHz (PCS). However, theexact design of the parasitic element 10 forms no essential part of theinvention. FIG. 2 is only showing an exemplifying embodiment and is notconsidered to limit the scope of the invention.

By printing the antenna pattern on the main PCB, the antenna is alwayspositioned in the same position every time. Therefore, the mechanicaltolerances involved with the connection of an antenna known in the artto the PCB can be substantially eliminated, which also improves theperformance of the antenna. For example, a bad connection between thecircuits of the PCB and the antenna will not occur and the antennapattern will always be positioned in exactly the same position inrelation to the signal source.

As is known to the man skilled in the art, it is preferred to provide aground plane under the antenna pattern of a PIFA antenna. Therefore, theextended ground plane 11 having a first and second end, respectively, isprovided essentially parallel to the PCB, and positioned opposite theantenna pattern at the second side of the PCB 7. This will also providegood radiation characteristics of the antenna, e.g. by directing theradiation in a preferred direction. The size of the extended groundplane 11 is at least as big as the size of the antenna pattern, and theshape of said plane 11 corresponds essentially to the shape of saidpattern. A smaller extended ground plane 11 is possible, however it willhave a negative effect on the bandwidth of the antenna.

The distance between the PCB 7 and the extended ground plane 11 ispreferably in the range of 6–10 mm. A smaller distance will decrease thebandwidth of the antenna, and a larger distance is not necessary andwill only effect the dimensions of the antenna. In this embodiment, theextended ground plane 11 comprises a metal layer mounted on a carrier,such as a piece of dielectric material. However, other configurations ofconductive material, which can provide a ground plane 11 can beutilized. The material of the extended ground plane 11 should have goodreflection properties of electromagnetic radiation, such as copper. Thiswill direct the radiation of the antenna in a preferred direction andthe antenna efficiency will increase.

As can be seen in FIG. 2, the first end of the extended ground plane 11is connected to the ground plane of the main PCB 7 through a distanceportion 12, which will provide sufficient distance between the extendedground plane 11 and the PCB 7. Also, the distance portion 12 willprovide connection between the extended ground plane 11 and the groundplane of the PCB 7. A first end of the distance portion 12 is connectedto the PCB 7, preferably at the connection point of the parasiticelement 10 to the ground plane of the PCB 7, as can be seen in FIG. 2,and is extending substantially orthogonal from the second side of thePCB 7. However, other angles are also possible as long as sufficientdistance between the PCB 7 and the extended ground plane 11 is obtained.A second end of the distance portion 12 is connected to the first end ofthe extended ground plane 11. In the first embodiment, the distanceportion 12 is made of a conductive material, such as copper, forconnecting the ground plane of the PCB 7 and the extended ground plane12. Also, it is possible that the distance portion 12 forms part of theextended ground plane 11, which then is provided e.g. as a bent metallayer.

To further improve the antenna characteristics, a second conductivelayer 14, similar to the first conductive layer of the extended groundplane 11, can as an option be provided substantially parallel to andopposite said first conductive layer of the extended ground plane 11 toform a microwave choke. This second layer 14 is also connected to thesecond end of the distance portion 12, and consequently to the groundplane of the main PCB 7. The second conductive layer has preferably thesame size and form as the first conductive layer and form a slottherewith. The distance between the conductive layers is small,preferably not more than 1 mm. Between the conductive layers is adielectric member 15 provided, e.g. in form of the support elementdescribed above.

Between the extended ground plane 11 and the PCB, it is possible toposition electronic components of the mobile telephone 1 having a lowprofile in the range of up to approximately 3 mm, such as a buzzer. Bypositioning suitable electronic components between the PCB 7 and theextended ground plane 11, the interior space of the mobile telephonewill be better utilized.

The first embodiment disclosed in FIG. 2 provides a small and efficientantenna, which is inexpensive to manufacture and provides good radiationcharacteristics in several frequency bands. A Smith chart and a SWR(standing wave ratio) diagram in FIG. 4 illustrate the performance of aprototype of the antenna in FIG. 2.

As is well known to the man skilled in the art, a SWR diagramillustrates the frequencies at which an antenna is resonating. The SWRdiagram of FIG. 4 represents the return loss in dB as a function offrequency. The lower dB values in a SWR diagram, the better. In a SWRdiagram, a resonance is an area, within which the return loss is low (ahigh negative value in dB). In the SWR diagram of FIG. 4 this looks looklike steep and deep cavities. As is apparent, the antenna according tothe invention has good resonating properties in the GSM band at around880–960 MHz, the DCS band at around 1710–1880 MHz, and the PCS band ataround 1850–1990 MHz.

Briefly speaking, in the Smith chart of FIG. 4 the circles representdifferent frequencies, in which the antenna of FIG. 2 is operating. Thehorizontal axis represents pure resistance (no reactance). Of particularimportance is the point at 50 Ω (the middle of the horizontal axis),which normally represents an ideal input impedance. As can be seen inFIG. 4, the first embodiment of the antenna is tuned to have an inputimpedance of 50 Ω without any impedance matching circuit.

As is mentioned previously, the specific design of the antenna patternis not fundamental to the present invention. The design of the antennapattern is different in each individual case to tune the antenna in apreferred frequency band. To illustrate this, a second alternativeembodiment of the inventive antenna is disclosed in FIG. 3. Again, thePCB 27 is shown as ending at the beginning of the antenna pattern, as inFIG. 2. However, as is apparent to the man skilled in the art, this isonly for illustrative purposes. In a real application the PCB 27 extendsover the full extension of the entire antenna pattern, as the antennapattern is printed on the PCB 27.

The built-in printed multi-port antenna comprises in a similar fashionas the multi-band antenna in FIG. 2 an antenna pattern printed on themain PCB 27 of the mobile telephone 1. However, the antenna pattern ofthe multi-port antenna comprises different antenna arms for differentfrequency bands and each Rx and Tx.

The multi-port antenna is a dual-band antenna having four multi-portantenna arms 28, 29, 30, 31, i.e. two for the lower frequency band andtwo for the higher frequency band. In this embodiment no parasiticelement is provided. However, the man skilled in the art easilyimplements this by providing a dual-layer PCB with a parasitic elementprinted on the PCB 27 opposite the main antenna pattern. Also, themulti-port antenna comprises an extended ground plane 25 having one, ortwo (not shown), conductive layers similarly to the first embodiment inFIG. 2, connected to the main ground plane of the PCB 27.

Each of the multi-port antenna arms 28, 29, 30, 31 are connected to Rxand Tx ports 32, 33, 34, 35, respectively, of the PCB 27 by connectionstrips, as described above.

The present invention has been described above with reference to a firstembodiment and an alternative embodiment. However, many alternativeembodiments not described herein are equally possible within the scopeof the invention, as defined by the appended independent claims.Particularly as regards the specific geometrical dimensioning of thepattern of conductive material, which makes up the antenna, the variousdimensions will have to be carefully selected depending on the actualapplication. Moreover, the frequency bands in which the antenna isoperative may also be greatly varied depending on the actualapplication. Therefore, the antenna pattern has to be tuned for theactual application, which is believed to be routine actions by the manskilled in the art and is therefore not further disclosed herein.

In the drawings, some of the dimensions and the distance betweendifferent parts of the antenna, such as the distance between the PCB 7,27 and the extended ground plane 11, 25, are highly exaggerated forillustrative purposes, and are not to be considered effecting the scopeof the invention.

1. A built-in antenna for use in a portable electronic communicationapparatus, the antenna comprising: an antenna pattern of a conductivematerial printed on a Printed Circuit Board (PCB) having a ground plane;and an extended ground plane comprising at least one conductive layer,which is connected to the ground plane of the PCB, the extended groundplane being arranged at a distance from and substantially parallel tothe PCB and opposite the antenna pattern.
 2. The antenna according toclaim 1, wherein the conductive layer is connected to the ground planeof the PCB via a distance portion having a first end connected to theground plane of the PCB and extending substantially orthogonal away fromthe PCB, and a second end connected to the conductive layer of theextended ground plane.
 3. The antenna according to claim 2, wherein thedistance portion comprises metal.
 4. The antenna according to claim 3,wherein the at least one conductive layer and the distance portion eachcomprise copper.
 5. The antenna according to claim 1, wherein the sizeof the extended ground plane at least corresponds to the size of theantenna pattern, and the shape of the extended ground plane correspondsto the shape of the antenna pattern.
 6. The antenna according to claim1, wherein the distance between the PCB and the extended ground plane isin a range of 6–10 mm.
 7. The antenna according to claim 1, wherein theextended ground plane comprises a second conductive layer positionedparallel and opposite to a first conductive layer, said secondconductive layer is connected to the ground plane of the PCB, and thesize and the shape of said second conductive layer correspond to thesize and shape of the first conductive layer.
 8. The antenna accordingto claim 7, wherein a dielectric member having a thickness of not morethan 1 mm is positioned between the first and the second conductivelayers of the extended ground plane.
 9. The antenna according to claim1, wherein the at least one conductive layer comprises metal.
 10. Theantenna according to claim 1, wherein the portable electroniccommunication apparatus comprises a mobile telephone.
 11. The antennaaccording to claim 1 wherein the extended ground plane is spaced apartfrom the Printed Circuit Board (PCB).
 12. A portable electroniccommunication apparatus for use in a wireless telecommunication system,the portable electronic communication apparatus comprising: a built-inantenna comprising an antenna pattern of a conductive material printedon a Printed Circuit Board (PCB) having a ground plane, and an extendedground plane comprising at least one conductive layer, which isconnected to the ground plane of the PCB, the extended ground planebeing arranged at a distance from and substantially parallel to the PCBand opposite the antenna pattern; and radio frequency (RF) circuitrycoupled to the built-in antenna.
 13. The portable electroniccommunication apparatus according to claim 12, wherein the conductivelayer is connected to the ground plane of the PCB via a distance portionhaving a first end connected to the ground plane of the PCB andextending substantially orthogonal away from the PCB, and a second endconnected to the conductive layer of the extended ground plane.
 14. Theportable electronic communication apparatus according to claim 13,wherein the distance portion comprises metal.
 15. The portableelectronic communication apparatus according to claim 14, wherein the atleast one conductive layer and the distance portion each comprisecopper.
 16. The portable electronic communication apparatus according toclaim 12, wherein the size of the extended ground plane at leastcorresponds to the size of the antenna pattern, and the shape of theextended ground plane corresponds to the shape of the antenna pattern.17. The portable electronic communication apparatus according to claim12, wherein the distance between the PCB and the extended ground planeis in a range of 6–10 mm.
 18. The portable electronic communicationapparatus according to claim 12, wherein the extended ground planecomprises a second conductive layer positioned parallel and opposite toa first conductive layer, said second conductive layer is connected tothe ground plane of the PCB, and the size and the shape of said secondconductive layer correspond to the size and shape of the firstconductive layer.
 19. The portable electronic communication apparatusaccording to claim 18, wherein a dielectric member having a thickness ofnot more than 1 mm is positioned between the first and the secondconductive layers of the extended ground plane.
 20. The portableelectronic communication apparatus according to claim 12, wherein the atleast one conductive layer comprises metal.
 21. The portable electroniccommunication apparatus according to claim 12, wherein the portableelectronic communications apparatus comprises a mobile telephone. 22.The portable electronic communication apparatus according to claim 12wherein the extended ground plane is spaced apart from the PrintedCircuit Board (PCT).